Physical Sciences Inc. (PSI), in partnership with clinicians in the Massachusetts General Hospital Department of Oral and Maxillofacial Surgery, proposes to continue development of an innovative device for performing distraction osteogenesis (DO) of the mandible. The concept under development uses miniature hydraulics in a fully buried actuator capable of producing linear and curvilinear distraction trajectories. This new distractor will reduce patient responsibility by automating the motion process, permit clinicians to alter the distraction rate of motion as treatment progresses, and reduce distraction time by making the motion virtually continuous. It will also offer the option of fully-buried placement, with no linkages or electrical connections passing through skin. Phase I demonstrated feasibility of the concept with bench top measurements and tests with the prototype implanted in a pig cadaver. All of the proposed Phase I objectives were completed, and the team was able to complete several development steps beyond the proposed Phase I effort. We propose herein to build on the initial success with a Phase II program that will refine the design, produce several prototypes, and perform testing in live animals. Though additional testing will be required, the Phase II work will develop all of the essential components necessary to produce a clinically-useful distractor.